1. Field of the Invention
The present invention relates to a casting film for producing a ceramic green sheet. More particularly, it is concerned with a casting film which is used in the production process of a ceramic green sheet in producing ceramic electronic part items, and which has excellent wettability of ceramic slurry and moderate releasability for the ceramic green sheet.
2. Description of the Related Arts
A ceramic electronic part item such as a capacitor, a laminated inductor element, a piezo-part, a thermistor and a varister is produced by a method comprising the steps of forming a green sheet by coating a casting film with ceramic slurry which is suited to the aforesaid electronic part items, which is used in high dielectric constant, magnetism and the like, and which is composed of ceramic powders, organic binders, plasticizers, solvents (an organic solvent or water) and the like (Step {circle around (1)}); equipping the resultant green sheet with an electrode made of palladium, silver, nickel or the like by means of screen printing (Step {circle around (2)}); thereafter peeling off the green sheet from the casting film and laminating the green sheets in multi-layer (Step {circle around (3)}); forming ceramic green chips through a step of press cutting (Step {circle around (4)}); baking the chips thus obtained (Step {circle around (5)}); and equipping the baked chips with terminal electrodes made of silver, silver palladium, nickel, copper or the like (Step {circle around (6)}). In addition thereto, there has recently been proposed a new production process in which the above-mentioned Steps {circle around (1)} and {circle around (2)} are repeated plural times, followed by the Step {circle around (3)} {refer to Japanese Patent Application Laid-Open No. 130150/1996(Heisei-8)}.
Accompanying miniaturization, weight-saving and improved performance of ceramic electronic parts in recent years, a thin-filmed green sheet is in rapid progress, and is required to have a film thickness of 4 μm or smaller. Conventional casting films wherein a silicone based releasing agent is used, however, give rise to a problem in that repelling is caused due to small thickness of coating in the case of applying ceramic slurry, thereby making it impossible to form a uniform coating. Hence, it is urged to develop a casting film imparted with favorable wettability of ceramic slurry. In addition, with regard to the above-mentioned multi-layering method by repeating the Steps {circle around (1)} and {circle around (2)} plural times, conventional casting films involve such a problem that excessive releasability thereof causes the green sheet firstly formed to be lifted or peel off from the casting film at the time of repeated coating of ceramic slurry on and after the second time, resulting in unfavorable practice of the multi-layer casting. Therefore, it is urged to develop a casting film imparted with moderate releasability from a green sheet.